Analysing level of harmonics in MV-networks to enhance newly designed function for real-time monitoring of residual current level in dispatch system

Increased capacitive earth fault currents due to the high level of cabling significantly increased demands for the safe and reliable operation of compensated networks. A high value of capacitive currents currently leads to an unknown alteration of residual current since the value of residual current is not being monitored in the dispatch system. The residual current serves as an essential parameter for estimating the touch and step voltage in the event of an earth fault and designing earthing systems. The results of the extended analysis proved that the present method for determining the residual current is no longer sufficient for ensuring the safe design of earthing systems. Thus, a new method for estimating the residual current is proposed based on the newly designed function that is embedded in the regulator of the arc-suppression coil. The new function presents an opportunity for real-time monitoring, even predicting, the estimated value of residual current in the dispatch system. However, the regulator of the arc-suppression coil can only calculate the value of the residual current for fundamental frequency, which does not comply with standards. Higher harmonics must be included in the designed function to estimate the real residual current. The main aim of this research paper is to present the results of an analysis that was conducted to determine the level of higher harmonics of residual current that were measured in the various compensated networks. The emphasis is also put on the possible automatization of the designed function for real-time monitoring of the residual current level in the dispatch system while considering possible situations that might happen in real distribution networks.